The invention relates to extraction of sealed flexible sachets containing at least one substance for the preparation of a beverage.
The use of pre-metered and pre-packaged portions of ground coffee for the preparation of expresso-type coffee has the advantage that it facilitates the operations to prepare the coffee while ensuring that the quality of the product is relatively consistent.
These portions are currently provided in two main forms.
According to a first general form, the portions disclosed in Swiss Patent No. 636 311, U.S. Pat. No. 5,012,629 and European Patent Application Publication No. 0 272 432 are formed by two sheets of filter paper sealed over their periphery and filled with ground coffee. This solution has the drawback that an oxygen-barrier outer packaging is required to prevent the oxidation of the product during storage. This outer packaging entails additional costs and a supplementary operation for the consumer who has to remove it before the desired coffee can be extracted.
According to a second form, disclosed in Application PCT/CH91/00 222, the portion is formed by a leak-tight capsule with a concave base opening into its extraction device by deformation under the action of the introduction of the extraction fluid, then perforation against pointed members. This capsule, formed by a leak-tight envelope forming a lateral wall and two walls, one of which forms the base of the cartridge and the other of which closes the opposite end of the cartridge, has the drawback that it makes simultaneous use of several different packaging materials, at least one of which has to be thick enough to make it semi-rigid. It can be used only in one direction with an extraction device which is completely adapted to the capsule and to its arrangement. Moreover, it is relatively bulky as the coffee is not compacted.